1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) without image sticking, ghost image and fan-out phenomenon when the LCD is turned off. More particularly, the present invention relates to a timing controller for the LCD and a signal control circuit and a method thereof.
2. Description of Related Art
Recently, thin film transistor liquid crystal displays (TFT-LCDs) have been widely used and have become one of a mainstream in the display market for substituting the cathode ray tube (CRT). With development of semiconductor technology, the TFT-LCD has been developed such advantages as low power consumption, smaller size and light weight, high resolution, high color saturation, and long lifespan, such that the TFT-LCD has been widely applied to electronic products closely related to our daily life, such as LCD monitors and LCD TVs.
FIG. 1 is a block diagram illustrating a driving mode of a conventional TFT-LCD. FIG. 2 is a diagram illustrating a driving waveform of the TFT-LCD of FIG. 1 when the TFT-LCD is turned off. Referring to FIG. 1 and FIG. 2, generally, a turning off process of the TFT-LCD includes the following steps. First, when supplying of a clock CLK and a data D of a low voltage differential signal (LVDS) from a bus 101 to a timing controller 103 stops, during a time interval between a time point A and a time point B on a timeline T, a driving signal TPO (generally is a TTL signal) required for driving data drivers (data driving ICs) 105a˜105n output from the timing controller 103 may be gradually decreased to a ground level GND. Next, when the driving signal TPO is gradually decreased to the ground level GND (i.e. after the time point B), the voltage level of a supply voltage VDD provided by a power supply unit 107 is decreased from a high voltage level H to the ground level GND. These steps are necessary for the turning off process of the TFT-LCD.
However, during the time interval between the time point A to the time point B, the driving signal TPO is in a state FRS without control (i.e. a free run state), and is still taken as an effective signal by the data driver 105a˜105n during this time interval. Therefore, the data driver 105a˜105n may still output a display data DD to an LCD panel 109 according to an image signal VD and a timing signal SCLK provided by the timing controller 103 before the TFT-LCD is turned off, and now an image displayed by the LCD panel 109 is a last frame of image displayed before the TFT-LCD is turned off, and this is the so-called image sticking phenomenon.
Moreover, since the voltage level of the supply voltage VDD provided by the power supply unit 107 may be decreased from the high voltage level H to the ground level GND only after the time point B, residual charges within a pixel array (not shown) of the LCD panel 109 may be gradually dissipated after the TFT-LCD is turned off. If a driving method of the LCD panel 109 is a line inversion driving method, charge dissipation will be performed when nearly a half of the pixels within the pixel array of the LCD panel 109 are in a high level, which may further lead to the so-called fan-out phenomenon of the LCD panel 109.
Therefore, if the driving mode of the TFT-LCD of FIG. 1 is applied, the image sticking and fan-out phenomenon may occur when the TFT-LCD is turned off, and liquid crystal molecules of the pixels within the LCD panel 109 may be deteriorated due to repetition of the above two phenomenon, which may result in a fact that a previous image may be retained each time when the LCD panel 109 displays a new image, which is the so-called ghost image phenomenon.